// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Data.Common;
using System.Diagnostics;
using System.Runtime.CompilerServices;
using JetBrains.Annotations;

namespace Microsoft.EntityFrameworkCore.Storage.Internal
{
    /// <summary>
    ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
    ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
    ///     any release. You should only use it directly in your code with extreme caution and knowing that
    ///     doing so can result in application failures when updating to a new Entity Framework Core release.
    /// </summary>
    public sealed class TypedRelationalValueBufferFactory : IRelationalValueBufferFactory
    {
        private readonly Func<DbDataReader, object[]> _valueFactory;

        /// <summary>
        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
        ///     any release. You should only use it directly in your code with extreme caution and knowing that
        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
        /// </summary>
        public TypedRelationalValueBufferFactory(
            [NotNull] RelationalValueBufferFactoryDependencies dependencies,
            [NotNull] Func<DbDataReader, object[]> valueFactory)
        {
            _valueFactory = valueFactory;
        }

        /// <summary>
        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
        ///     any release. You should only use it directly in your code with extreme caution and knowing that
        ///     doing so can result in application failures when updating to a new Entity Framework Core release.
        /// </summary>
        [MethodImpl(MethodImplOptions.AggressiveInlining)]
        public ValueBuffer Create(DbDataReader dataReader)
        {
            Debug.Assert(dataReader != null); // hot path

            var values = _valueFactory(dataReader);

            return values.Length == 0
                ? ValueBuffer.Empty
                : new ValueBuffer(values);
        }
    }
}
